Fake connection

I have installed ASA 5505 and placed FTP Server into DMZ Zone. When someone try to connect with FTP then it connects without having any issue. Same time I reviewed the logs which shows a connection making from outside to DMZ but after some time I see same connection get triggered from Inside Zone to DMZ Zone FTP Server but it uses same source and destination address which were using for DMZ and Outside and it reset all FTP connection . Please Advice!!!